This invention relates generally to wireless communications circuitry, and more particularly, to wireless communications circuitry for handheld electronic devices.
Handheld electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type.
Due in part to their mobile nature, handheld electronic devices are often provided with wireless communications capabilities. Handheld electronic devices may use wireless communications to communicate with wireless base stations. For example, cellular telephones may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz (e.g., the main Global System for Mobile Communications or GSM cellular telephone bands). Handheld electronic devices may also use other types of communications links. For example, handheld electronic devices may communicate using the WiFi® (IEEE 802.11) band at 2.4 GHz and the Bluetooth® band at 2.4 GHz.
To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices. For example, manufacturers have made attempts to miniaturize the antennas used in handheld electronic devices.
A typical antenna may be fabricated by patterning a metal layer on a circuit board substrate or may be formed from a sheet of thin metal using a foil stamping process. Many devices use planar inverted-F antennas (PIFAs). Planar inverted-F antennas are formed by locating a planar resonating element above a ground plane. These techniques can be used to produce antennas that fit within the tight confines of a compact handheld device.
To provide sufficient wireless coverage over all communications bands of interest, modern handheld electronic devices sometimes contain multiple antennas. For example, a modern handheld electronic device might have one antenna for handling cellular telephone communications in cellular telephone bands and another antenna for handling data communications in a data communications band. Although the operating frequencies of the cellular telephone antenna and the data communications antenna are different, there will still generally be a tendency for undesirable electromagnetic coupling between the antennas.
This electromagnetic coupling forms an undesirable type of signal interference. Unless the antennas are sufficiently isolated from each other, simultaneous antenna operation will not be possible.
Electromagnetic isolation between two antennas can often be obtained by placing the antennas as far apart as possible within the confines of the handheld electronic device. However, conventional spatial separation arrangements such as these are not always feasible. In some designs, layout constraints prevent the use of spatial separation for reducing antenna interference.
It would therefore be desirable to be able to provide improved ways in which to isolate antennas from each other in a handheld electronic device.